Download Terrestrial Planets` Formation Atmosphere

Planetary Science
Week 4: Introduction to
the Solar System
The Solar System
The Sun makes up 97% of the mass of the solar system.
Most of the rest is Jupiter and Saturn.
Almost all of the rest is Uranus and Neptune.
What is left, including Earth, is negligible.
Extremely important to us, but negligible nonetheless.
The Terrestrial
Planets
Mercury, Venus,
Earth, and Mars
are called
terrestrial because
they have a
compact, rocky
surface like the
Earth's. The
planets Venus,
Earth, and Mars
have significant
atmospheres
while Mercury
has almost none.
The Jovian Planets
Jupiter, Saturn,
Uranus, and Neptune
are known as the
Jovian (Jupiter-like)
planets, because they
are all gigantic
compared with Earth,
and they have a
gaseous nature like
Jupiter's. The Jovian
planets are also
referred to as the gas
giants, although some
or all of them might
have small solid cores.
Asteroids
Most located between orbits of Mars and
Jupiter, some Near Earth Asteroids.
Stony or metallic.
Dwarf planet Ceres.
Formation of the Solar System
1. Nebula collapses
Disk of material orbiting protostar
2. Accretion of planets through collisions
3. T Tauri Stage
Most hydrogen, helium and other volatiles are blown
away from the inner solar system by solar wind.
4. Inner planets are left with dense
rocky composition with little volatiles.
Outer planets have low density composition
with massive hydrogen and helium atmospheres.
Terrestrial Planets' Formation
Bombardment
During and following formation of
Terrestrial planets, catastrophic
bombardment by remaining rocky
planetesimals cratered surfaces of
planets
Terrestrial Planets' Formation
Energy Imparted
Impacting material gives up kinetic
energy, coupled with intense
radioactivity, produced sufficient heat to
melt and chemically differentiate planets
into layered structure of core, mantle,
and crust.
Terrestrial Planets' Formation
Differentiation
Heaviest elements, like Fe, separated
from lighter elements, such as O and Si
(primarily, silicates and oxides of Fe and
Mg) and sank toward the center Silicates
and oxides rose to form mantle
surrounding an iron-rich core. Lightest
materials rose to top and solidified as
crust.
Terrestrial Planets' Formation
Atmosphere
Atmospheres of Terrestrial planets
formed during this process and afterward
by outgassing from impacting material
and from hot interiors.
Jovian Planets' Formation
Within outer cooler regions of solar nebula, icy planetesimals collided,
building larger bodies of icy and rocky materials . As these bodies grew to a
mass a few times that of Earth, they attracted gravitationally hydrogen and
helium from surrounding gas.
Capture and retention of gaseous materials was easier far from Sun, where
temperatures were lower. Because of their great masses, Jupiter and to some
extent Saturn have kept very nearly same relative proportion of hydrogen
and helium to the heavier elements as has the Sun.
Uranus and Neptune were never massive enough to accrete hydrogen and
helium to any great extent; thus carbon, nitrogen, oxygen, silicon, and iron
dominate their compositions.
Contraction by Jupiter and Saturn during formation released great deal of
gravitational potential energy, heating them significantly.
Comets are probably a fossil relic of primordial icy planetesimals that existed
in outermost regions of solar nebula.
Mercury
Distance from Sun,
millions
36
Mean Diameter miles
3000
Period of sidereal
revolution
88
days
Period of rotation
59
days
# of satellites
Mass. Earth
considered as 1
0
0.0543
Escape Velocity, miles
per second
2
Mean density water =
1
5.3
Surface gravity Earth
=1
0.38
Mean orbital velocity,
miles per second
29.76
Venus
Distance from Sun,
millions
67
Mean Diameter
miles
7600
Period of sidereal
revolution
225
days
Period of rotation
243
days
# of satellites
0
Mass. Earth
considered as 1
0.8148
Escape Velocity,
miles per second
6.3
Mean density water
=1
4.95
Surface gravity
Earth = 1
0.87
Mean orbital
velocity, miles per
second
21.78
Earth
Distance from
Sun, millions
93
Mean Diameter
miles
7918
Period of sidereal
revolution
365.25
days
Period of rotation
23 hr
56 min
# of satellites
1
Mass. Earth
considered as 1
1.0000
Escape Velocity,
miles per second
6.95
Mean density
water = 1
5.52
Surface gravity
Earth = 1
1.00
Mean orbital
velocity, miles
per second
18.52
The Moon is the only natural
satellite of Earth:
Orbit: 384,400 km from Earth
Diameter: 3476 km
Mass: 7.35e22 kg
Mars
Distance from
Sun, millions
142
Mean Diameter
miles
4200
Period of sidereal
revolution
687
days
Period of rotation
24 hr
37 min
# of satellites
2
Mass. Earth
considered as 1
0.1069
Escape Velocity,
miles per second
3.1
Mean density
water = 1
3.95
Surface gravity
Earth = 1
0.39
Mean orbital
velocity, miles
per second
15.00
Mars' Satellites
Mars has two tiny satellites which
orbit very close to the surface:
PHOBOS
Distance from Surface: 9000km
Radius: 11000km,
Mass: 1.08e16kg
Discovered: Hall 1877
DEIMOS
Distance from Surface: 23000
Radius: 6000
Mass: 1.80e15
Discovered: Hall 1877
Jupiter
Distance from
Sun, millions
483
Mean Diameter
miles
87,000
Period of sidereal
revolution
12
years
Period of rotation
9 hr
50 min
# of satellites
61
Mass. Earth
considered as 1
318.35
Escape Velocity,
miles per second
37
Mean density
water = 1
1.33
Surface gravity
Earth = 1
2.65
Mean orbital
velocity, miles
per second
8.12
Jupiter has 61 known Satellites
(as of May 2003): the four large
Galilean moons, 23 smaller named
ones, plus many more small ones
discovered recently but not yet
named.
•Jupiter is very gradually slowing
down due to the tidal drag
produced by the Galilean satellites.
Also, the same tidal forces are
changing the orbits of the moons,
very slowly forcing them farther
from Jupiter.
•Io, Europa and Ganymede are
locked together in a 1:2:4 orbital
resonance and their orbits evolve
together. Callisto is almost part of
this as well. In a few hundred
million years, Callisto will be locked
in too, orbiting at exactly twice the
period of Ganymede (eight times
the period of Io).
Saturn
Distance from
Sun, millions
886
Mean Diameter
miles
72,000
Period of sidereal
revolution
29.5
years
Period of rotation
10 hr
14 min
# of satellites
31
Mass. Earth
considered as 1
95.3
Escape Velocity,
miles per second
22
Mean density
water = 1
0.69
Surface gravity
Earth = 1
1.17
Mean orbital
velocity, miles
per second
6.00
# Rings
7
Saturn has 18 named
satellites plus 13 recently
discovered and as yet
unnamed ones:
• Pan
• Atlas
• Prometheus
• Pandora
• Epimetheus
• Janus
• Mimas
• Enceladus
• Tethys
• Telesto
• Calypso
• Dione
• Helene
• Rhea
• Titan
• Hyperion
• Iapetus
• Phoebe
Uranus
Distance from
Sun, millions
1780
Mean Diameter
miles
33,200
Period of
sidereal
revolution
84
years
Period of
rotation
10 hr
45 min
# of satellites
21
Mass. Earth
considered as 1
14.58
Escape Velocity,
miles per second
13
Mean density
water = 1
1.56
Surface gravity
Earth = 1
1.05
Mean orbital
velocity, miles
per second
4.23
Uranus' Satellites
Uranus has 20 named moons (plus 1 recently discovered one which as yet has
not been given an official name).
•They form three distinct classes: the 11 small very dark inner ones discovered
by Voyager 2, the 5 large ones (below), and the newly discovered much more
distant ones.
•Most have nearly circular orbits in the plane of Uranus' equator (and hence at a
large angle to the plane of the ecliptic); the outer 4 are much more elliptical.
Neptune
Distance from
Sun, millions
2790
Mean Diameter
miles
31,000
Period of sidereal
revolution
165
years
Period of rotation
15 hr
48 min
Number of
satellites
11
Mass. Earth
considered as 1
17.26
Escape Velocity,
miles per second
15
Mean density
water = 1
2.27
Surface gravity
Earth = 1
1.23
Mean orbital
velocity, miles per
second
3.37
Neptune's Satellites
Neptune has 11 known moons; 7
small named ones and Triton
plus three more discovered
recently which have yet to be
named.
Naiad
Thalassa
Despina
Galatea
Larissa
Proteus
Triton
Nereid
Triton
Pluto
Distance from Sun,
millions
3670
Mean Diameter
miles
4000
Period of sidereal
revolution
248
years
Period of rotation
?
# of satellites
2
Mass. Earth
considered as 1
0.1?
Escape Velocity,
miles per second
?
Mean density water
=1
5?
Surface gravity
Earth = 1
0.5?
Mean orbital
velocity, miles per
second
2.95
Pluto is now classified as a dwarf planet. This is the
clearest view yet of distant Pluto and its moon,
Charon, as revealed by NASA's Hubble Space
Telescope. The Hubble observations show that
Charon is bluer than Pluto. This means that both
worlds have different surface composition and
structure. A bright highlight on Pluto suggests it has a
smoothly reflecting surface layer.
Comets, Asteroid and Meteoroids
• Comet: Small icy body that orbits the sun.
• Asteroid: Small, rocky planetary body orbiting the sun.
• Meteoroid: Meteorite before reaching a planet (Asteroid or
Comet).
• Meteor: A Meteorite in transit through a planets atmosphere.
• Meteorite: Any particle of solid matter that has fallen to a
planets (or moons) surface.
Comets
Unlike the other small bodies in the
solar system, comets have been known since
antiquity. There are Chinese records of Comet Halley
going back to at least 240 BC. The famous Bayeux
Tapestry, which commemorates the Norman Conquest
of England in 1066, depicts an apparition of Comet
Halley. As of 1995, 878 comets have been catalogued
and their orbits at least roughly calculated. Of these
184 are periodic comets (orbital periods less than 200
years); some of the remainder are no doubt periodic
as well, but their orbits have not been determined with
sufficient accuracy to tell for sure. Comets are
sometimes called dirty snowballs or icy mudballs.
They are a mixture of ices (both water and frozen
gases) and dust that for some reason didn't get
incorporated into planets when the solar system was
formed. This makes them very interesting as samples
of the early history of the solar system.
Asteroids are rocky and metallic objects that orbit the Sun
but are too small to be considered planets. They are known as minor
planets. Asteroids range in size from Ceres, which has a diameter of
about 1000 km, down to the size of pebbles. Sixteen asteroids have
a diameter of 240 km or greater. They have been found inside
Earth's orbit to beyond Saturn's orbit. Most, however, are contained
within a main belt that exists between the orbits of Mars and Jupiter.
Some have orbits that cross Earth's path and some have even hit the
Earth in times past. One of the best preserved examples is the
Barringer Meteor Crater near Winslow, Arizona.
Asteroids are material left over from the formation of the solar
system. One theory suggests that they are the remains of a planet
that was destroyed in a massive collision long ago. More likely,
asteroids are material that never coalesced into a planet. In fact, if
the estimated total mass of all asteroids was gathered into a single
object, the object would be less than 1,500 km (932 mi) across -less than half the diameter of our Moon.
Berringer Meteor Crater
Impact at Winslow, AZ
The Asteroid Belt
Asteroids are rocky and metallic
objects that orbit the Sun but are
too small to be considered planets.
They are known as minor planets.
The Majority of the asteroids lie in
a belt between Mars and Jupiter.
The Asteroid Belt
Asteroids are material that never
coalesced into a planet. In fact, if the
estimated total mass of all asteroids was
gathered into a single object, the object
would be less than 1,500 kilometers
(932 miles) across – less than half the
diameter of our moon.